The goal of this proposal is to investigate the molecular mechanisms of signal transduction in the mammalian vomeronasal chemoreception in mice and voles will be used as a model system, since their reproductive physiology and behavior is strongly influenced by pheromonal cues and putative pheromone receptors have been discovered and characterized. Previous studies indicate that microvillar membranes detached from the apical dendrites of porcine vomeronasal neurons are enriched in adenylate cyclase and phospholipase C, and that the application of boar urine and seminar fluid to microfillar vomeronasal juvenile females causes production of inositol triphosphate via A Gq-related. This application proposes to: 1. Map the signal transduction mechanisms in the vomeronasal organ of female mice and pine voles: 2. Fractionate by male urine by high pressure liquid chromatography and purify pheromones that stimulate phospholipase C in microvillar membranes from female vomeronasal organs; 3. Identify a vomeronasal microvillar membrane proteins that undergo pheromone-induced phosphorylation through a G- protein coupled receptor kinase to provide insights in the regulation of pheromonal signal transduction. The proposed studies will provide the first molecular description. The proposed studies will provide desensitization process of reproductive pheromones in mammalian vomeronasal neurons. In addition they will provide specific ligands for some of the identified putative pheromone receptors.